According to one estimate, 63 per cent of men and 54 per cent of women are in their current long-term relationships because their current partner “poached” them from a previous partner. Now researchers in the US and Australia have conducted the first investigation into the fate of relationships formed this way, as compared with relationships formed by two unattached individuals.

An initial study involved surveying 138 heterosexual participants (average age 20; 71 per cent were women) four times over nine weeks. All were in current romantic relationships that had lasted so far from 0 to 36 months. Men and women who said they’d been poached by their current partner tended to start out the study by reporting less commitment to their existing relationship, feeling less satisfied in it, committing more acts of infidelity and looking out for more alternatives.What’s more, over the course of the study, these participants reported progressively lower levels of commitment and satisfaction in their relationships. They also showed continued interest in other potential romantic partners and persistent levels of infidelity. This is in contrast to participants who hadn’t been poached by their partners – they showed less interest in romantic alternatives over time.

The researchers led by Joshua Foster attempted to replicate these results with a second sample of 140 heterosexual participants who were surveyed six times over ten weeks. Again the participants who said they’d been poached by their partners tended to report less commitment and satisfaction in their current relationships, and more interest in romantic alternatives. However, unlike the first sample, this group did not show deterioration in their relationship over the course of the study. The researchers speculated this may be because the study was too short-lived or because deterioration in these relationships had already bottomed out.

It makes intuitive sense that people who were poached by their partners showed less commitment and satisfaction in their existing relationship. After all, if they were willing to abandon a partner in the past, why should they not be willing or even keen to do so again? This logic was borne out by a final study of 219 more heterosexual participants who answered questions not just about the way their current relationship had been formed, but also about their personalities and attitudes.

Foster and his team summarised the findings: “individuals who were successfully mate poached by their current partners tend[ed] to be socially passive, not particularly nice to others, careless and irresponsible, and narcissistic. They also tend[ed] to desire and engage in sexual behaviour outside of the confines of committed relationships.” The last factor in particular (measured formally with the “Socio-sexual Orientation Inventory-revised”) appeared to explain a large part of the link between having been poached by one’s partner and having weak commitment to the new relationship.

Across the three studies, between 10 and 30 per cent of participants said they’d been poached by their current partners. This shows again that a significant proportion of relationships are formed this way, the researchers said, and that more research is needed to better understand how these relationships function. “We present the first known evidence [showing] specific long-term disadvantages for individuals involved in relations that formed via mate poaching,” they concluded.